1. Field of the Invention
The present invention relates to a white road line recognition device for a vehicle that recognizes a white road line based on an image captured by an onboard camera.
2. Description of the Related Art
For the improvement of vehicle safety, driving support devices have recently been developed that actively support driver's operations. In order to achieve a function such as lane deviation prevention, a driving support device generally recognizes a white road line based on a captured image in front of an own vehicle, etc., and makes an estimation on an own lane based on the captured white road line.
As a technology that recognizes the white road line, for, example, Japanese Unexamined Patent Application Publication No. 1999-85999 (hereunder referred to as “Patent Document 1”) discloses a technology that recognizes a white road line of a complicated shape such as multiple white road line (double white road line) that has a solid line for separating lanes and a dashed line for visual guidance. This technology detects in a road image an edge point where luminance changes from dark to light (positive edge point) and an edge point where luminance changes from light to dark (negative edge point) and executes a Hough transform to the positive and negative edge points respectively to a search Hough space corresponding to the positive and negative edge points respectively.
The visual guidance line of the double white road line, which is the inner line thereof, is sometimes comprised of diamond markings that are placed at a specified interval, lying in a dashed line. When this special type of double white road line or the like is recognized, edge points of the visual guidance line (diamond markings) are arranged discontinuously in a different direction from an extending direction of the double white road line. Accordingly, when only the Hough transform is executed to the edge points of the inner visual guidance line upon the recognition of the double white road line or the like, the direction of a resultant line may be different from the extending direction of the actual lane.
On the other hand, as disclosed Patent Document 1, upon the recognition of the double white road line or the like, a line extending along in a proper direction may be obtained for the double white road line with the special visual guidance line or the like by detecting positive edge points and negative edge points for both the inner line and outer line (visual guidance line and lane division line). However, the detection of edge points for the plural lines upon the recognition of the double white road line may excessively increase calculation load.
Accordingly, in view of the above, it is an object of the present invention to provide a white road line recognition device for a vehicle that obtains a stable recognition result even for a multiple white road line or the like without a calculation process such as edge point detection being complicated.